Suction box for papermaking apparatus



Nov. 10, 1970 K. LoPAs 3,539,448

SUCTION BOX FOR PAPERMAKING APPARATUS Filed April 19, 1968 s Sheets-Sheet 1 INVENTOR. KAS/M/R LOP/LS BY BLAIR, BUG/(LES, CESAR/ 87f OIVGE ATTORNEYS NOV. 10, 1970 oP s 3,539,448

SUCTION BOX FOR PAPERMAKING APPARATUS Filed April 19, 1968 3 Sheets-Sheet 2 INVENTOR. KAS/M/R LOPAS BY BLA/R, BUG/(LES, CESAR/ f 57: ONGE ATTORNEYS Nov. 10, 1970 op s 3,539,448

SUCTION BOX FOR PAPERMAKING APPARATUS Filed April 19, 1968 7 3 Sheets-Sheet 3 INVEN'I'OR. KAS/M/R LOP/LS BY BLAIR, BUG/(L Es, CESAR/ 5: M65

ATTORNEYS United States Patent 3,539,448 SUCTION BOX FOR PAPERMAKING APPARATUS Kasimir Lopas, 118 Skyview Drive, Stamford, Conn. 06902 Filed Apr. 19, 1968, Ser. No. 722,680 Int. Cl. D21f l/52 U.S. Cl. 162-364 9 Claims ABSTRACT OF THE DISCLOSURE The suction box disclosed is for use in the Foudrinier section of a papermaking apparatus. A receptacle with a perforate top is provided with upper and lower chambers connected by one or more throttle valves actuated by floats. A partial vacuum is maintained in the interior of the suction box to withdraw liquid from the paper stock on the Foudrinier section. A liquid drainage conduit which acts as a siphon provides drainage from the lower chamber to a reservoir below the section; it is preferably of a length which can be maintained full of liquid by air pressure on the reservoir. A vacuum source may also be connected with the conduit to remove entrapped air and facilitate the filling thereof with liquid.

BACKGROUND OF THE INVENTION In the process of making paper from fibrous stock, the stock in a water suspension is ejected from a headbox, as described in my copending application Ser. No. 699,551 filed Jan. 22, 1968, and onto a moving screen or Foudrinier wire. The wire forms part of the Foudrinier section of a papermaking apparatus. The stock suspension being carried on the Foudrinier wire is spread out in sheet form and then dried sufiiciently for further processing into a finished paper product.

Heretofore, the drying of paper stock on a Foudrinier wire has been accomplished in part with conventional suction boxes; these are box-like devices, a plurality of which are spaced at intervals along the Foudrinier section with their tops under the stock carrying surface of the wire. The tops of the suction boxes are perforate and the interor is maintained at a pressure sufficiently below atmospheric pressure so that water in the paper stock is drawn into the box as the stock passes overhead on the Foundrinier wire.

The water withdrawn from the stock in the prior art apparatus has flowed through the suction boxes and into a deep trough or water pan under the Foundrinier section When the pan becomes full, the water overflows and drains into a reservoir for disposal or recirculation. A problem arises, however, in that drainage from the pan is slow in comparison to the volume of water being extracted from the stock by the suction boxes, particularly in larger papermaking machines. Drainage from the pan can be increased by permitting a substantial depth or head of water to accumulate therein; however, the weight of the quantity of water required is great, and added to the weight of the pan itself has necessitated very heavy structural support for the Foudrinier section. This has increased the cost of manufacture and placed limitations on the location of such machinery.

Accordingly, representative objects of the present invention are to produce a suction box which is reliable, economical and effective in use, and which has a high rate of liquid drainage without requiring a water pan under the Foudrinier section.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions 3,539,448 Patented Nov. 10, 1970 hereinafter set forth, and the scope of the invention will be indicated in the claims.

SUMMARY OF THE INVENTION The present invention relates to an improved suction box for use in papermaking apparatus and, more particularly, for use in conjunction with the Foudrinier section of such apparatus.

In use, a plurality of the suction boxes of the invention are spaced along the length of a Foudrinier section under the wire, and progressively withdraw liquid from a paper stock suspension carried thereon. In general, each suction box comprises a receptacle of box-like configuration positioned just under the stock carrying portion of the Foudrinier wire. The top of each receptacle is perforate, and its interior is connected with a vacuum pump or similar vacuum source so that a partial vacuum is produced therein. The partial vacuum causes water to be withdrawn from the stock suspension passing overhead.

The interior of each suction box is further divided into upper and lower chambers to contain the water withdrawn from the stock suspension. Liquid flow between the two chambers is controlled by a plurality of throttle valves, each of which responds to a rise in the liquid level in the upper chamber by gradually opening to increase the flow from the upper chamber to the lower chamber. In this manner the Water in the upper chamber may be maintained at a predetermined and substantially constant small volume while the lower chamber is kept full.

The lower chamber of the suction box is connected to a conduit through which the Water can drain into a reservoir remote from the Foudrinier section. The conduit outlet is preferably below the Water level in the reservoir. Further, the dimensions of the conduit are preferably such that it will be maintained full of water during normal operation of the papermaking apparatus. The conduit thus functions as a siphon to provide rapid drainage from the suction box.

For optimum drainage at a high rate, the conduit should have a vertical leg having a length approximating the maximum height of a column of water which can be supported within the conduit solely by atmospheric pressure. This optimum height or barometric length, as the term is used herein in the specification and claims, should preferably not be exceeded as this may cause the siphon eifect to be broken and result in slow drainage from the suction box. Where optimum drainage conditions are not required, however, a conduit of less than barometric length may be used.

The suction box of the invention thus overcomes the problems of the prior art discussed above. In particular,

because of the rapid drainage afforded by the structure of the invention, the need for a pan under the Foudrinier section is eliminated. This eliminates the excess Weight associated with the prior art apparatus and enables the use of lighter and lower cost structural support. The savings in weight also enables greater flexibility to be achieved in the location of each Foudrinier section.

BRIEF DESCRIPTION OF THE DRAWINGS 0 of the suction box of the invention.

FIG. 3 is a sectional view taken along line 33 of FIG. 2.

FIG. 4 is an enlarged top plan view of a throttle valve in the suction box.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4.

Similar reference characters refer to similar parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown a representative 'Foudrinier section in a papermaking apparatus. Section 10 comprises a headbox 12 from which a paper stock suspension is distributed in a constant stream from a nozzle or slice 14 onto a moving Foudrinier wire 16. Wire 16 is formed in a continuous loop which runs over a breast roll 18 and a couch roll 20 positioned at either end of the section support frame 22. Between breast roll 18 and couch roll 20 the wire 16 is supported on a plurality of table rolls 24 spaced along the length of the support frame 22. The return path of wire 16 is controlled by a plurality of wire rolls 26 over which wire 16 passes under the Foudrinier section 10. A plurality of tensioning rolls 28 which are biased against wire 16 between the wire rolls 26 maintain the proper degree of tension in wire 16 for efficient operation.

Still referring to FIG. 1, the suction boxes 30- of the invention are spaced along frame 22, between the table rolls 24 and under the stock carrying surface of wire 16. A conduit 32, more fully described below, extends down from each suction box 30 and has an outlet 34 positioned below the water level 36 in a reservoir 38 under section 10. Conduits 32 provide drainage from the suction boxes 30 for the water extracted from the stock suspension carried on wire 16.

More specifically, with reference to FIG. 2, each suction box 30 comprises a box-like receptacle 40 of preferably tapered cross-section ('FIG. 3) and having a perforate plate 42 forming the top thereof. Perforate plate 42 is positioned under wire 16 to permit the water withdrawn from the paper stock to pass into receptacle 40.

A port 44 is provided at one end of receptacle 40. A vacuum pump or similar vacuum source (not shown) is connected with port 44 so that a partial vacuum may be formed within the interior of receptacle 40' to extract the liquid from the stock suspension carried on wire 16. The strength of the partial vacuum formed within receptacle 40 will depend upon the location of the particular suction box on the Foudrinier section. With reference to FIG. 1, suction boxes which are nearest to the breast roll 18 require only a low degree of vacuum since the Water content of the paper stock is initially high and can be readily extracted. The degree of partial vacuum within individual suction boxes 30, however, should be increased as they approach the couch roll 20 to extract the ever decreasing amount of liquid in the paper stock suspension. Typically, the degree of vacuum in the suction boxes of the invention will vary from about 1 to 2 inches of mercury for those closest to breast roll 18 to about 8 to 10 inches of mercury in those closest to couch roll 20.

Referring back to FIG. 2, the interior of receptacle 40, due to its tapered shape (FIG. 3), is divided into a large volume upper chamber 46 and a low volume lower chamber 48 by a horizontal partition 50'. At least one and preferably a plurality of apertures 52 are provided in partition 50 and communicate with both the upper 46 and the lower 48 chambers in receptacle 40. As shown in FIGS. 4 and 5, a scoop-like enclosure 54 comprising a sloping top plate 56 and side walls 58 and 60 surrounds each aperture 52. Enclosure 54 is open at one end 62 to permit the passage of water from upper chamber 46, through aperture 52 and into lower chamber 48.

Each aperture 52 and its partially surrounding enclosure 54 form part of a throttle valve for restricting the flow of water from upper chamber 46 to lower chamber 48 in a manner more fully described below. The balance of each throttle valve comprises at least one, but preferably a pair of arms 64 and 66, each respectively pivotally mounted at one end on a pin 68, 70 secured in the end of a rod 72 afiixed to top plate 66 of enclosure 54 as shown in FIG. 4. Arms 64 and 66 straddle enclosure 54 and are secured at their free ends to a float 74 (FIGS. 4 and 5) which is made of a material which will float in the liquid being withdrawn from the paper stock.

Referring to FIG. 5, arms 64 and 66 carry a baffle plate 76 transversely secured between them. Plate 76 is so positioned that it gradually obstructs the open end 62 of enclosure 54 when float 74 drops in response to a lowering liquid level in upper chamber 46. Baffle plate 76 thus serves to check the flow of liquid between upper chamber 46 and lower chamber 48 when the liquid level in chamber 46 drops, and to increase the flow when the liquid level in chamber 46 rises. Accordingly, a relatively constant liquid level is maintained in upper chamber 46, typically 1 to 2 inches, while the low volume lower chamber 48 is kept full of water to sustain the desired siphon effect discussed above.

Referring again to FIG. 2, a conduit 32 formed of tubing communicates with lower chamber 48 at one end 78 thereof. Conduit 32 has an outlet 34 positioned below the water surface 36 in a reservoir 38 which is under Foudrinier section 10 as shown in FIG. 1. As discussed above, conduit 32 should be maintained full of water to provide the desired siphon effect for a high rate of drainage from within suction box 30. To facilitate the filling of conduit 32 with water and to prevent the formation of air bubbles therein, a vent 80- is provided at its upper end adjacent suction box 30. A high vacuum source (not shown) may be connected with vent 80 to withdraw entrapped air from within conduit 32.

As further discussed above, conduit 32 should have a substantially vertical leg 32a (FIG. 2) of barometric lengt when it is desirable to have optimum high rate drainage from suction box 30. The barometric length, however, will vary with the cross-section of the conduit. As an example, it has been found that a conduit formed of cylindrical pipe having a diameter of approximately 2.5 inches and with a vertical leg having a length of approximately 30 to 35 feet (barometric length for this diameter pipe) will provide optimum drainage from the suction box of the invention.

OPERATION OF SUCTION BOX In operation, the interior of suction box 30 is evacuated to the desired degree of vacuum through port 44. The pressure differential then existing between the outer surface of wire 16 and the interior of suction box 30 causes liquid from the stock suspension on wire 16 to be drawn down through the openings in perforated top 42 (FIG. 2). The liquid withdrawn from the stock suspension thus begins to fill the upper chamber 46 of suction box 30.

Preferably, when put into operation, lower chamber 48 and conduit 32 are already filled with liquid from previous operation of the apparatus so that a siphon effect is already present. However, if lower chamber 48 and conduit 32 are empty or partially empty due to drainage they may have to be filled with liquid, i.e., primed before operation is begun.

As upper chamber 46 gradually begins to fill with liquid, each float 74 begins to rise lifting arms 64 and 66 and attached bafiie plate 76 so that the open end 62 of each enclosure 54 is gradually uncovered. Liquid is thus permitted to flow from upper chamber 46 through aperture 52 into lower chamber 48 until a substantial equilibrium is established between the flow from the stock suspension into upper chamber 46, and the flow from upper chamber 46 out through lower chamber 48 and conduit 32 into reservoir 38.

It can be seen from FIG. 2 that any sudden increase in water level in upper chamber 46 will immediately elevate the float 74 at that point and permit increased drainage from upper chamber 46 to lower chamber 48 until equilibrium is re-established. For this reason, it is preferable to have a plurality of throttle valves spaced along the length of partition 50 (FIG. 2) so that equilibrium may be quickly re-established whenever the flow of liquid from the paper stock varies over the length of suction box 30.

The positioning and size of bafile plate 76 may be adjusted so that a predetermined area of opening 62 (FIG. 5) is uncovered at any given water level in upper chamber 46. In this manner, the liquid level in upper chamber 46 may be kept to a predetermined small volume to minimize the weight of liquid constantly maintained in suction box 30.

Baffle 76 is also preferably arranged to close opening 62 before the liquid is fully drained from upper chamber 46. In this way, lower chamber 48 is kept substantially closed-01f from atmospheric pressure. Under these conditions, conduit 32 and lower chamber 48 will remain full of liquid due to the eifect of atmospheric pressure on the surface 36 of the liquid in reservoir 38, so long as the vertical leg 32a is kept at a barometric length or less. Conduit 32 is thus maintained as a siphon to provide rapid drainage from within suction box 30.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efiiciently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

:1. A suction box for papermaking apparatus comprising, in combination:

(A) a receptacle (1) having a top open to the passage of liquid therethrough and (2) a partition dividing said receptacle into upper and lower chamber,

(B) means forming a partial vacuum in the interior of said receptacle,

(C) throttle valve means on said partition (1) communicating with said upper and lower chambers and (2) responsive to a rise or fall in the liquid level in said upper chamber to respectively increase or decrease the liquid flow between said upper and lower chambers whereby a relatively constant liquid level is maintained in said upper chamber, and

(D) liquid drainage conduit means (1) communicating with said lower chamber and (2) having an outlet below the level of said lower chamber whereby liquid may be rapidly drained from within said receptacle.

2. A suction box as defined in claim 1 wherein said conduit means has a substantially vertical leg of a barometric length between said lower chamber and said outlet to provide optimum high rate drainage from within said receptacle.

3. A suction box as defined in claim 1 including vacuum means for withdrawing air from within said conduit means to facilitate the filling thereof with liquid.

4. A suction box as defined in claim 1 wherein said throttle valve means comprises at least one aperture through said partition, at least one arm pivotally supported at one end for substantially vertical movement adjacent said aperture and secured to a float at the other free end thereof, and means carried by said arm for gradually uncovering said aperture in response to upward vertical movement of said arm.

5. A suction box as defined in claim 4 including a plurality of said throttle valve means spaced along the length of said partition.

6. In combination with a Foudrinier section in papermaking apparatus, liquid removal means comprising, in combination:

(A) a plurality of suction boxes spaced along the length of the apparatus, each said suction box comprising (1) a receptacle (a) having a top open to the passage of liquid therethrough, said top being positioned under and adjacent the stock carrying surface of the Foudrinier wire, and

(b) a partition dividing said receptacle into upper and lower chambers,

(2) means forming a partial vacuum in the interior of said receptacle,

(3) a plurality of spaced throttle valves on said on said partition, each said valve comprising (a) an aperture through said partition communicating with said upper and lower chambers,

(b) at least one arm pivotally supported at one end for substantially vertical movement adjacent said aperture and secured to a float at the other free end thereof and (c) means carried by said arm for gradually uncovering said aperture in response to upward vertical movement of said arm, and

(4) a liquid drainage conduit communicating with said lower chamber and having an outlet at a point below the level of said lower chamber.

7. An apparatus as defined in claim 6 wherein said liquid drainage conduit has a substantially vertical leg therein between said lower chamber and said outlet, said leg being of a barometric length to provide optimum high rate drainage from within said receptacle.

8. An apparatus as defined in claim 6 including vacuum means communicating with said conduit for withdrawing air from within said conduit to facilitate the filling thereof with liquid.

9. An apparatus as defined in claim 6 wherein said aperture is surrounded by a scoop open only at one end and projecting into said upper chamber, and including a bafile plate carried by said arm and positioned to gradually uncover the open end of said scoop as said arm is pivoted vertically upward by the action of said float in response to a rising liquid level in said upper chamber.

References Cited UNITED STATES PATENTS 2,264,169 11/1941 Poirier 162364 X 3,266,975 8/1966 Cribben 162364 X REUBEN FRIEDMAN, Primary Examiner T. A. GRANGER, Assistant Examiner US. Cl. X.R. 162374 

